Found out today that if you have the 2005 6-disc changer, you can hold the SSP button down and change your vehicle type between tC, xA. and xB. Changes the sound quality a whole lot between car models. I personally like the xA output better than the tC.
If this has been posted previously, my apologies. Search was going slow and said it didn't return anything, so
I feel the hammer coming down on you quickly..but it has been covered many a time, but I am glad that you found that out, the xA version is a lot better, and you don't have to have the cd changer to do it